This invention concerns joystick controllers and more particularly joystick controllers used to control X, Y and Z axis motion of a powered element, such as the probe shaft of a coordinate measuring machine, or the cutting tool of a three axis machine tool.
Coordinate measurement machines are known which utilize a probe shaft mounted for vertical movement on a carriage (referenced as Z axis motion), which carriage in turn is mounted for movement along two orthogonal axes in a horizontal plane (referenced as X--Y motion).
The probe shaft is provided with a tip which is adapted to contact points on an object supported on a table surface and, as the probe tip is moved along the X, Y, and Z-axes, measurements of the object are achieved by transducer means measuring this movement along each axis.
In some machines, the probe is powered to be driven to move from point to point about the object to be measured and it is necessary to provide a controller for the operator if the motion is manually controlled.
Joystick controllers have heretofore been known in which pivoting of a joystick shaft in either of two orthogonal directions produces corresponding X--Y movement of the probe shaft. A separate controller has been used to produce up-down motion of the probe shaft. Since the operator needs to activate a "record" button and operate two separate controllers, the process is somewhat cumbersome. Three axis controllers are also known in which a rotary motion is utilized to achieve a Z axis motion. In this instance, there is not instinctive corresponding movement of the controller joystick and the probe shaft, requiring significant experience for operator proficiency to be achieved.
With such controllers, it is necessary that a null position be reliably repeatable with a reasonable degree of accuracy and some means must be provided to preclude inadvertent motion in two axes as the joystick moves in the third direction.